Liquid electrostatic developers having chargeable toner particles dispersed in an insulating nonpolar liquid are well known in the art and are used to develop latent electrostatic images. Ideally, such liquid developers should be replenishable in the particular equipment in which they are used since developer solids that are removed by the imaging process must be replaced in order to maintain image quality. Failure to replace the solids used will result in image defects, such as low print density.
In general, high solids concentration toners are used because relatively low concentrations (e.g., in the range of 10 to 15% by weight solids) result in greater liquid buildup in the equipment, which then must be removed and disposed of as hazardous waste. Thus, it is desirable to initially use a toner containing less liquid, and to maintain working strength by replenishing the developer from a separate source located within the equipment, thus minimizing the undesirable accumulation of carrier liquid in the equipment.
When toners are present in the liquid developer in more concentrated form, however, they become difficult to redisperse in the carrier. For example, aggregates may be formed. This can cause serious problems in the replenishment of the liquid developer in the equipment being used.